Visual field changes as an early indicator of glioblastoma multiforme progression: two cases of functional vision changes before MRI detection.

Glioblastoma multiforme is an aggressive tumor associated with a high rate of recurrence even after maximal therapy. In a disease with poor prognosis and rapid deterioration, early detection of tumor progression is necessary to make timely treatment decisions or to initiate end of life care. We identify two cases where Humphrey visual field testing predated magnetic resonance imaging and positron emission tomography findings of tumor progression by months in glioblastoma multiforme. New or worsening visual field defects may indicate signs of tumor progression in glioblastoma multiforme and should prompt further investigation.